1. Field of the Invention
The present invention relates to an ink jet recording sheet. More particularly the present invention relates to an ink jet recording sheet having an ink receiving layer coated on a substrate with high adhesion, having a recording surface with a high gloss and capable of recording thereon ink images having a high clarity with a high ink drying property.
2. Description of the Related Art
In an ink jet recording system, desired ink images are recorded on a recording sheet by jetting imagewise fine drops of an ink from an ink jetting nozzle toward a recording surface of the recording sheet to cause the jetted ink drops to be absorbed imagewise in the recording sheet. Printers using the ink jet recording system are appropriately utilized for color printing and are advantageous in that the sizes of the printers are small and the prices of the printers are lower than that of printers using other recording systems.
Currently, since the performances of personal computers have significantly improved and multimedia functions have become widespread, a demand for printing documents including colored images or colored photographs in office or home has been promoted. For this demand, color printer using the ink jet recording system are considered to be very useful output printers.
As a conventional recording sheet usable for the ink jet recording system, a recording sheet produced by coating a surface of a substrate paper sheet with an ink-absorbing resin, or a mixture of a pigment selected from various types of pigments with a water-soluble resin or latex resin, to form an ink receiving layer, and optionally smoothing the surface of the ink receiving layer by, for example, a supercalender treatment, is employed. The conventional recording sheet is, however, disadvantageous in that since the surface of substrate paper sheet is rough due to the pulp fibers located in the surface portion of the sheet, and has an unsatisfactory smoothness, the resultant recording sheet exhibits an insufficient gloss. Also, when the conventional recording sheet is subjected to an ink jet recording procedure, the ink-absorbed portions of the printed sheet expand and thus the printed sheet is roughened and wavy.
In view of the poor performance of the substrate paper sheet, a polyolefin-coated sheet in which both the surfaces of a base paper sheet are coated with a polyolefin resin, for example, as polyethylene resin, or a plastic resin film, for example, a polyester film is employed in place of the paper sheet, as a substrate sheet for the ink jet recording sheet. As reported in Japanese Unexamined Patent Publications No. 4-216,990 and No. 7-32,723, when this type of the substrate sheet is coated with an ink receiving layer, the resultant ink jet recording sheet is evaluated at a certain high level.
Namely, the polyolefin-laminated substrate sheet or the plastic resin film has a high smoothness and thus the resultant ink jet recording sheet exhibits a high gloss.
However, since the polyolefin-laminating layer or the polyester resin film are hydrophobic, generally, the resultant hydrophobic substrate sheet has a surface having a poor affinity to the ink receiving layer and thus when an aqueous coating liquid for the ink receiving layer is applied onto the hydrophobic surface of the substrate sheet, a repelling phenomenon, for the coating liquid, occurs on the substrate sheet surface to form coating defects in the resultant ink receiving layer, or the resultant ink receiving layer exhibits a poor adhesion to the substrate sheet.
To prevent the above-mentioned disadvantages, before the coating of the substrate sheet with the coating liquid for the ink receiving layer, a surface-activating treatment, for example, a corona discharge treatment, is applied to the substrate sheet surface, and an undercoat layer comprising a water-soluble resin, as a principle component, is formed on the substrate sheet. These pre-treatments are not satisfactory for the ink jet recording sheet for practical use.
Accordingly, there is a strong demand for an ink jet recording sheet in which an ink receiving layer""is firmly bonded to a substrate consisting of a polyolefin-laminated paper sheet with a high adhesion.
When the polyolefin-laminated paper sheet is employed as a substrate sheet for an ink jet recording sheet, there is another disadvantage in that a curling phenomenon occurs.
Generally, the ink jet recording sheet for practical use must have a good appearance and must pass easily through a printer. To satisfy these requirements, the recording sheet preferably has a certain curling property. In the usual use environment, the recording sheet must be flat or be slightly curled in a convex shape. This form is referred to as a back-curling form. After printing, when the printed sheet is observed, if the front surface, namely, the ink receiving layer surface is curled in the form of a concave, which form is referred to as a top-curling form, observation is difficult and the appearance of the curled sheet is bad. Also, when the curled sheet in the top-curling form is attached at the back surface thereof on a wall surface, the edge portions of the sheet are spaced from the wall surface and cannot be stably attached to the wall surface. Also, when the ink jet recording sheets having a top-curling property are subjected to a printing procedure, the sheets cannot travel through the printer and cannot be accurately printed. Thus, the recording sheet must be in a flat form or in a slightly convexed form which form is referred to as a slightly.
The ink receiving layer usually expands or shrinks due to the change in temperature and humidity of the environment. Thus, even when a recording sheet exhibits a desired curling property under a specific environmental conditions, it may exhibit a high top-curling property under a low temperature low humidity condition, or a high back-curling property under a high temperature high humidity condition. These properties may cause the recording sheets to be difficult to use in practice.
The curling property can be reduced to a certain extent by increasing the thickness and the rigidity of the sheet. However, the thick recording sheets have a bad appearance and a high price and thus are not suitable for practical use.
Various attempts were made to obtain a desired curling properties. However, a desired ink jet recording sheet having both the high gloss and the desired curling property has not yet been obtained.
Japanese Unexamined Patent Publication No. 8-269,900 discloses a support for image-carrying material, which comprises a base sheet made from a paper sheet comprising as a principal component, a natural pulp, a film-forming resin layer covering a surface of the base sheet on which surface an image-forming layer is formed, and a polyolefin coating layer covering the opposite surface of the base sheet. The support is wound in the form of a roll. In this roll, the support is wound in such a manner that the image-forming layer becomes outside surface layer and the resultant roll is stored at a temperature of 20xc2x0 C. or more. However, in this support, only the curling property is fixed by storing the polyolefin resin-coated sheet substrate at a specific temperature. Thus, even if a desired curling property is obtained in specific circumstances, when the circumstances change, it is difficult to restrict the resultant curling phenomenon.
Japanese Unexamined Patent Publication No. 6-171,206 discloses an ink jet recording sheet comprising a support with at least one type of ink receiving layer formed on a front surface of the surface and at least one back-coat layer formed on a back surface of the support. The recording sheet is characterized in that the backcoat layer comprises a pigment and a binder, as principal components, and the pigment has an average equilibrium moisture content of 1.9 to 5.5%. In this recording sheet, the support is formed from a paper sheet made from, as principal component materials, a wood pulp such as a chemical pulp, mechanical pulp or waste paper pulp and a conventional pigment, or a coated paper sheet comprising a paper sheet and polyolefin resin layers covering the paper sheet, or a film. The back-coat layer comprises a pigment of, for example, precipitated calcium carbonate, ground calcium carbonate, kaolin, and talc, and a binder, for example, polyvinyl alcohol, polyvinyl acetate, oxidized starch etherified starch, and cellulose derivatives, for example, carboxymethyl cellulose, and hydroxyethylcellulose. The backcoat layer comprising the pigment and the binder as principal components, is, however, disadvantageous in that the curling-restricting effect thereof is low. Thus, to obtain a satisfactory curling-restricting effect, the coating layer must be formed to a very large thickness.
Japanese Unexamined Patent Publication No. 6-171,207 discloses an ink jet recording sheet having a support comprising mainly a wood pulp and a pigment, at least one ink receiving layer formed on a front surface of the support, and at least one backcoat layer formed on the back surface of the support, and characterized in that a binder for the backcoat layer comprises a synthetic polymer latex having a glass transition temperature of xe2x88x9250xc2x0 C. to +25xc2x0 C., as an indispensable component, and a water-soluble binder comprising at least one member selected from starch, polyvinyl alcohol and cellulose derivatives. The support is made from a paper sheet produced from a wood pulp such as chemical pulp, mechanical pulp and waste paper pulp and a conventional pigment, as principal components. This type of the ink jet recording sheet is, however, disadvantageous in that the curl-restricting property is insufficient, and a high gloss appropriate for full colored ink images cannot be obtained because the paper sheet support has a rough surface and, when the ink is absorbed, the ink jet recording sheet surface is roughened by the absorbed ink.
Japanese Unexamined Patent Publication No. 5-286,228 discloses a recording sheet having a coloring matter-absorbing layer formed on a support material, wherein a polymer layer having a high water-swelling property is formed on a surface of the support material opposite to the surface on which the coloring matter-absorbing layer is formed. The support material is formed from sheets of plastic resins, for example polyester resins such as polyethylene terephthalate resin and polyester diacetate, and fluorine-containing resins such as ETFF. Also, the materials for the high swelling polymer layer is selected from, for example, polyvinyl alcohol, polyvinyl pyrrolidone and mixtures thereof. However, since the polyvinyl alcohol or polyvinylpyrrolidone absorb moisture and exhibit a tackiness, the resultant ink jet recording sheets may cause a blocking phenomenon in the printer.
Japanese Unexamined Patent Publication No. 5-96,843 discloses a recording sheet comprising an ink receiving layer, a base sheet, a heat-absorbing layer and an anti-curling layer. The base sheet is selected from transparent films of polymeric materials, for example, polyesters, polycarbonates, polysulfones, cellulose triacetate, polyvinyl chloride, viscose rayon (cellophane: trademark), and polyvinyl fluoride; flat paper sheet, for example, diazo paper sheet, opaque polymeric films and filler-filled polymer sheets. The heat-absorbing layer is formed from, for example, a vinylidene fluoride-hexafluoropropylene-copolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer or a vinylidene-tetrafluoroethylene-propylene copolymer. The anti-curling layer is formed from, for example, hydroxyporpylmethlcellulose, hydroxybutylmethylcellulose, hydroxyethylmethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, a carboxymethylcellulose salt and a caboxymethylhydroxyethylcellulose salt or methylcellulose.
However, the materials for the heat-absorbing layer are selected without consideration of the close adhesion between the polyolefin resin-coated back surface of the substrate sheet and the backcoat layer. Further, in a high humidity environment, the recording sheet exhibits an insufficient resistance to curling.
Generally, for the ink jet recording system, an aqueous ink is used in consideration of the high quality of the recorded images and of the high safety. The aqueous ink comprises a coloring material, for example, a dye or a coloring pigment, a polyhydric alcohol for preventing blocking of ink-jetting nozzles and another additive, dissolved or dispersed in a water medium.
The recording sheet for the ink jet recording system includes conventional wood-free paper sheets and specific ink jet recording sheets, for example, ink jet recording paper sheets having an ink receiving layer formed on a substrate paper sheet; gloss ink jet recording sheets having a gloss layer formed on the ink receiving layer; OHP ink jet recording sheets having an ink receiving layer formed on a transparent polyester film substrate; gloss ink jet recording sheets having an ink receiving layer formed on a white-colored polyester film substrate; synthetic paper ink jet recording sheets having an ink receiving layer formed on a synthetic paper substrate, photographic sheet-like ink jet recording sheets having a substrate comprising polyethylene resin-laminating layers formed on a paper sheet substrate and a ink receiving layer on the polyethylene resin-laminating layer of the substrate.
Currently, an ink jet printer or ink jet plotter which can record thereon high accuracy ink images similar to silver salt photographic images at high speed is developed and is available at a low price. For example, the ink jet recording system is included in digital cameras and scanners for the office or the home and is used for outputting the images and is used for business uses, for example, electric decoration signboards and a production of trade samples, for printing uses, for example, a production of printing plate material, for design uses, for example, printing of design images, for example, various colored images. For these uses, the ink jet recording sheet capable of recording thereon silver salt photographic image-like ink images having a surface gloss and an appearance similar to those of the silver salt photographic images, is in demand. The photograph support-like ink jet recording sheet is usually prepared by forming an ink receiving layer on a resin-coated paper sheet made by coating both the front and back surfaces of a substrate paper sheet with a polyethylene resin composition. The resin-coated paper sheet having polyethylene resin coating layers formed on the two surfaces of the substrate paper sheet does not allow an ink to permeate into the sheet because the polyethylene resin is hydrophobic, and is free from a cockling phenomenon which is generated when a paper sheet absorbs ink drops, has a high flatness, a low roughness and a high smoothness in comparison with these of the pulp paper sheets, for example, a wood-free paper sheet. Therefore, the resin-coated paper sheet is advantageously employed to produce an ink jet recording sheet having a high gloss and capable of recording thereon accurate ink images and the resultant ink jet recording sheet exhibits a silver salt photographic printing sheet-like hand.
The photographic printing sheet-like ink jet recording sheets are classified into two groups. The first group of recording sheets have an ink receiving layer comprising a resin composition containing, as a principal component, a resin having a capability of absorbing the ink usable for the ink jet recording. Thus, immediate after the printing, the ink receiving layer is swollen by the absorbed ink. The second group of recording sheets has an ink receiving layer comprising a pigment-binder composition comprising, as a principal component, a pigment capable of absorbing the ink used for the ink jet recording. In this case, immediate after the printing, the ink is absorbed in the internal pores formed in the particles of the pigment and in the gaps formed between the pigment particles each other. The former type of ink jet recording sheet is referred to as a swelling type recording sheet, and latter type of ink jet recording sheet is referred to as a space-absorbing type recording sheet.
The swelling type ink jet recording sheets are generally advantageous in that a high gloss can be relatively easily obtained and the production cost is low, but disadvantageous in that the water resistance of the recording sheets is low. Compared with this, the space-absorbing type ink jet recording sheets are advantageous in the high water resistance thereof but are disadvantageous in that a high gloss is difficult to obtain, and/or, specific materials are necessary for forming the ink receiving layer, and the production cost is high.
In the present invention, a swelling type ink receiving layer is advantageously utilized.
The swelling type ink receiving layer contains, as a principal component resin capable of absorbing the ink usable for the ink jet recording, at least one member selected from, for example, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl acetal, carboxymethylcellulose, hyudroxyethylcellulose, hydroxypropylmethylcellulose, polyethylene glycol, polyethyleneoxide, starch, casein and gelatin, and optionally, a cationic ink-fixing agent for fixing the absorbed ink, a pigment filler for preventing a blocking phenomenon, a surfactant, a fluorescent brightening agent and/or a viscosity-modifier is contained in the ink receiving layer.
The ink receiving layer containing, as a principal component, the ink-absorbing resin, is usually hydrophilic and thus generally exhibits an insufficient adhesion to a substrate sheet in which a substrate paper sheet is coated with a hydrophobic, water-nonabsorbing polyolefin resin. To solve this problem, the surface of the polyolefin resin coating layer is surface-activated by, for example, a corona discharge treatment before coating the ink receiving layer, or the ink receiving layer is added with a material having a high affinity to the polyolefin resin. However, these conventional means are insufficient to enhance the adhesion of the ink receiving layer to the polyolefin resin coating layer to a high level. Even if the adhesion is enhanced, the above-mentioned conventional means may cause the ink-absorbing property of the ink receiving layer to be degraded, or the printed ink images may be blotted or the curl-preventing property may be degraded.
Also, even if, before printing is applied, the adhesion of the substrate sheet to the ink receiving layer is good, after printing, the ink-absorbed portions of the ink receiving layer exhibits a reduced adhesion to the substrate sheet and, thus, when a small force is applied to the printed sheet, scratching damage is formed on the ink receiving layer, or the ink receiving layer locally slippes on the substrate sheet and thus the appearance of the printed sheet is significantly degraded. The possibility of generation of the above-mentioned phenomenon increases with an increase in the content of a polyhydric alcohol having a high boiling temperature and a high resistance to vaporization in the ink applied to the ink receiving layer and/or with an increase in the amount of the ink applied to the ink receiving layer per unit area of the ink receiving layer.
In the ink jet recording sheet having, as a substrate sheet, a polyolefin resin-coated paper sheet or a plastic resin film, for example, a polyester resin film, which is hydrophobic and has no ink-absorbing capacity, the above-mentioned problem in adhesion of the substrate sheet to the ink receiving layer occurs. To solve this problem, various attempts have been made. Namely, an anchor layer may be arranged between the substrate sheet and the ink receiving layer. Alternatively, the ink receiving layer may be formed in a two or more layered structure.
Various types of anchor layers have been formed between the polyolefin resin coated substrate sheet and the ink receiving layer. For example, Japanese Unexamined Patent Publication No. 7-32,723 discloses an ink jet recording sheet having an ink receiving layer formed on a polyolefin resin-coated sheet having a specific rigidity. In an example disclosed in the publication, the polyolefin resin-coated sheet was subjected to a corona discharge treatment and, then, an intermediate layer comprising gelatin, a curing agent and a surfactant was coated in an amount of 0.1 g/m2 on the corona discharge-treated surface, and an ink receiving layer comprising silica, colloidal silica, polyvinyl alcohol, a fixing agent, and a surfactant was coated in an amount of 10 g/m2 on the intermediate layer. The ink jet recording sheet produced by the above-mentioned method is advantageous in that no cockling phenomenon occurs but is disadvantageous in that the ink receiving layer has a low gloss and is not appropriate to record colored images with a high accuracy.
Japanese Unexamined Patent Publication No. 60-46,289 discloses a recording sheet having a water-soluble polymer-coated layer formed on a water-nonabsorbing support, and an anchor coat layer formed between the support and the coated layer and comprising, as a principal component, a water-soluble copolyester resin. The water-soluble copolyester resin-containing anchor coat layer may be applied to the polyolefin resin-coating layer of the substrate sheet. In this case, even if the polyolefin resin-coating layer can be coated with the anchor coat layer with a high adhesion, the adhesion between the anchor coat layer and the ink receiving layer may be insufficient, or the applied ink may be accumulated in a boundary between the anchor coat layer and the ink receiving layer and the ink images may be blotted, or the ink receiving layer may locally slip on the polyolefin resin-coated substrate sheet due to a small external physical force. Namely, the above-mentioned ink jet recording sheet failed to solve the above-mentioned problems.
Japanese Unexamined Patent Publication No. 61-237,682 discloses an ink jet recording sheet having a hydrophobic material layer formed on an ink receiving layer. In this recording sheet, the ink receiving layer is formed in a two-layered structure. The first layer is formed from a hydrophilic polymer and coated with a second layer formed from a polymer having a hydrophilicity equal to or lower than that of the first layer. The first (under) layer has a high ink-holding property and the second (upper) layer serves as an ink-permeating layer through which the ink is allowed to rapidly pass or as a protecting layer for the under layer. To improve the mechanical strength of the ink receiving layer or the adhesion between the ink receiving layer and the substrate sheet, the ink receiving layer optionally contains an SBR latex, a NBR latex, polyvinylformal, polymethyl methacrylate, polyvinyl butyral, polyacrylonitrile, polyvinyl chloride, polyvinyl acetate, a phenol resin or an alkyl resin. However, when these polymers are employed together with the hydrophilic polymer, the resultant ink receiving layer is deteriorated in the ink-absorbing property, the ink drying property and the resistance to ink-blotting, while the adhesion of the ink receiving layer to the substrate sheet is improved.
Japanese Unexamined Patent Publication No. 62-134,287 discloses an ink jet recording sheet having a substrate material and an ink receiving layer formed on the substrate material. The ink receiving layer may have a single-layer structure or a two-layered structure having a first (under) layer formed from a hydrophilic polymer and a second (upper) layer formed from a polymer having a hydrophilicity equal to or lower than that of the first layer. As an anchor coat layer, a layer comprising a curable resin composition comprising a mixture of a reactive or cross-linkable polyester resin, polyamide resin, or acrylic resin with an appropriate cross-linking agent, or a polyhalogenated vinyl resin is disclosed. The anchor coat layer may contribute to enhancing the adhesion between the polyolefin resin-coating layer and the anchor coat layer. However, the anchor coat layer causes the ink receiving layer to exhibit a low adhesion to the anchor coat layer, or the applied ink is accumulated in the boundary between the anchor coat layer and the ink receiving layer and thus the printed ink images are blotted, or the ink receiving layer locally slips on the polyolefin resin coated substrate sheet due to a small external physical force applied to the ink receiving layer. Namely, the ink jet recording sheet fails to solve the above-mentioned problems.
Japanese Unexamined Patent Publication No. 62-152,779 discloses an ink jet recording sheet comprising two or more-layered coating layer formed on a substrate material, wherein an upper layer in the coating layer exhibits a higher ink-absorbing rate than that of an under layer in the coating layer. The ink jet recording layer comprises a water-soluble or hydrophilic polymeric material, for example, gelatin, casein, starch, a polyamide, a polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol or a cellulose derivative. When the ink-absorbing rate of the upper layer is controlled to be higher than that of the under layer, the resultant ink receiving layer exhibits an improved resistance to blotting of ink images. However, when the above-mentioned type of ink receiving layer is formed on the polyolefin resin-coated substrate material, the adhesion between the ink receiving layer and the substrate sheet may be insufficient, or when a solvent component contained in the ink jet recording ink has a low vaporizing property, the ink can fully penetrate into the ink receiving layer and thus, after a certain time has passed, the adhesion of the ink-absorbed portions of the ink receiving layer to the substrate sheet is degraded. Thus, the ink jet recording sheet fails to solve the above-mentioned problems.
Japanese Unexamined Patent Publication No. 9-1924 discloses an ink jet recording sheet having an ink receiving layer formed on a support, wherein the ink receiving layer is a two- or more-layered structure. With respect to the two or more component layers in the ink receiving layer of the recording sheet, the closer the location of a component layer to the support, the relatively higher the affinity of a polymer contained in the layer to a high boiling temperature solvent contained in the ink applied to the ink receiving layer, and the closer the location of a component layer to the outermost surface of the ink receiving layer, the relatively lower the affinity of a polymer contained in the component layer to the high boiling temperature solvent contained in the ink. However, when a polymer having a high affinity to the high boiling temperature solvent in the ink is contained in a component layer close to the support, after the printing is completed, a large portion of the absorbed ink is located in the location close to the support, and thus the applied ink images exhibits a low drying rate and thus the ink recording layer may locally slip on the polyolefin resin-coated substrate layer.
As mentioned above, when an ink receiving layer is formed on a substrate sheet formed from a polyolefin resin-coated paper sheet or a polyester film which is hydrophobic and exhibits no ink-absorbing property, various attempts have been made to improve the adhesion between the ink receiving layer and the substrate sheet. However, target ink jet recording sheets satisfactory in all of high gloss, high smoothness, high ink-absorbing property, high ink drying rate and high resistance to ink-blotting; capable of recording thereon ink images having a high color density, a high clarity and a high accuracy, and exhibiting a high adhesion between the substrate sheet and the ink receiving layer not only before the printing but also after the printing, have not yet been obtained.
An object of the present invention is to provide an ink jet recording sheet having a high gloss, an excellent adhesion between a polyolefin resin-coated substrate sheet and an ink receiving layer formed on the substrate sheet, a high ink drying rate and being capable of recording thereon ink images having a high uniformity.
The above-mentioned object can be attained by the ink jet recording sheet of the present invention which comprises a substrate comprising a base paper sheet and a polyolefin laminate layer formed by extrusion-laminating a polyolefin resin composition on at least a front surface of the base paper sheet; and an ink receiving layer formed on a surface of the polyolefin laminate layer of the substrate,
wherein the surface of the polyolefin laminate layer is finely roughened and exhibits a center-line mean roughness (Ra) of 0.1 to 10 xcexcm, determined in accordance with Japanese Industrial Standard B 0601-1982.
In the ink jet recording sheet of the present invention, the surface of the ink receiving layer preferably exhibits 75xc2x0 specular glossiness of 30% or more, determined in accordance with Japanese Industrial Standard P8142-1993.
In the above-mentioned ink jet recording sheet of the present invention, the ink receiving layer preferably comprises at least one ink absorbing polymer selected from the group consisting of polyvinyl alcohol, cation-modified polyvinyl alcohols, polyvinyl pyrrolidone, cation-modified polyvinyl pyrrolidones, gelatin, phthalic acid-modified gelatins, casein, soybean casein, carboxyl-modified soybean caseins, starch, oxidized starchs, esterified starchs, phosphate-esterified starchs, carboxymethylcelluloce, hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, and water-dispersible vinyl acetate copolymers.
In the ink jet recording sheet of the present invention, the finely roughened surface of the polyolefin laminate layer is preferably formed by bringing a extrusion-laminated polyolefin resin composition layer on the base paper sheet into contact with a peripheral surface of a cooling roll, to thereby adjusting the center-line mean roughness (Ra) of the resultant polyolefin laminate layer to 0.1 to 10 xcexcm, determined in accordance with Japanese Industrial Standard B 0601-1982.
In the ink jet recording sheet of the present invention, optionally a backcoat layer is further formed on a back surface side of the substrate on which no ink receiving layer is formed, and a back-side intermediate layer is further formed between the back surface of the substrate and the backcoat layer to firmly bond the backcoat layer to the substrate therethrough.
In the ink jet recording sheet of the present invention, the backcoat layer preferably comprises at least one cellulose compound.
In the ink jet recording sheet of the present invention, the cellulose compound for the backcoat layer is preferably selected from the group consisting of cellulose nitrate,/cellulose acetate, cellulose acetate isopropionate, cellulose acetate butyrate, methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylhydroxyethylcellulose, carboxymethylhydroxyethylcellulose salts and carboxymethylcellulose salts.
In the ink jet recording sheet of the present invention, the back-side intermediate layer is preferably present in an amount of 0.001 to 1.0 g/m2.
In the ink jet recording sheet of the present invention, the back-side intermediate layer preferably comprises an adhesive polymeric material selected from the group comprising hydrophilic polymeric materials and latices of water-insoluble polymeric materials.
The ink jet recording sheet of the present invention, optionally, further comprises a front-side intermediate layer formed between the polyolefin laminate layer of the substrate and the ink receiving layer, comprising at least one polymeric material selected from the group consisting of gelatin, polyvinyl alcohol and cation-modified polyvinyl alcohols, and exhibiting an ink absorption capacity of 0.1 ml/g or more, but less than 1.5 ml/g; and the ink receiving layer formed on the front-side intermediate layer exhibits an ink absorption capacity of 1.5 ml/g or more, but less than 10 ml/g.
In the ink jet recording sheet of the present invention, the ink drying rate, which is represented by a time between a stage at which ink images are ink jet-recorded on an ink jet recording sheet and a stage at which no transfer of the ink in the recorded ink images on the ink jet recording sheet to a wood-free paper sheet superposed on the ink jet recording sheet under pressure is found, of 50 minutes or less.
In the ink jet recording sheet of the present invention, preferably the front-side intermediate layer is present in an amount of 0.01 to 0.5 gl/m2, and the ink receiving layer formed on the front-side intermediate layer is present in an amount of 3 to 50 g/m2.
In the ink jet recording sheet of the present invention, the ink receiving layer preferably comprises at least one member selected from the group consisting of hydroxypropylmethylcellulose and polyvinyl pyrrolidone.
In the ink jet recording sheet of the present invention, the hydroxypropylmethylcellulose for the ink receiving layer preferably has a degree of substitution, which means, in glucose ring units of cellulose, an average number of hydroxyl groups substituted by methoxy group, of 1.5 or more.
In the ink jet recording sheet of the present invention, the ink receiving layer comprises a mixture of hydroxypropylmethylcellulose and polyvinyl pyrrolidone, in a mixing weight ratio of 100:10 to 100:150.